1. Field of the Invention
The present invention relates to the field of electronics, and more particularly, to data storage devices.
2. Description of the Related Art
Computer systems generally use so called main memory comprised of semiconductor devices typically having the attribute that the devices can be randomly written to and read from with comparable and very fast access times (i.e., hundreds of nanoseconds) and thus are commonly referred to as random access memories. However, since semiconductor memories are relatively expensive, other higher density and lower cost memories (such as magnetic disk systems) may be used. Magnetic disk storage systems generally have access times that are on the order of tens of milliseconds. Disk storage may be used to store large quantities of data which can be sequentially transferred to main memory as needed. Another type of disk like storage is solid state disk storage (SSD, also called a solid state drive). SSD is a data storage device that uses memory chips, such as SDRAM, to store data, instead of the spinning platters found in conventional hard disk drives.
The term “SSD” can be used to refer to two different kinds of products. The first type of SSD, based on fast, volatile memory such as SDRAM, is categorized by fast data access and is used primarily to accelerate applications that may be held back by the latency of disk drives. Since this type of SSD uses volatile memory, it typically incorporates internal battery and backup disk systems to ensure data persistence. If power is lost for whatever reason, the battery can keep the unit powered long enough to copy all data from RAM to backup disk. Upon the restoration of power, data is copied from the backup disk to RAM and the SSD may resume normal operation. The first type of SSD can be especially useful on a computer which already may have the maximum amount of RAM. A second type of SSD can use flash memory to store data and is generally used as a replacement for a hard disk drive.